1. Field of the Invention
The present invention relates to electrically heated smoking devices, and particularly to systems and methods for supplying electrical power to the electrically heated smoking devices from a lithium ion power source.
2. Description of Related Art
Lithium ion battery technology was introduced in the mid-nineteen nineties. Lithium ion batteries are rechargeable and do not exhibit memory effect which is common in other rechargeable batteries. Memory effect is a condition that occurs in some rechargeable batteries when the battery is not fully discharged before recharging. The battery remembers the amount of energy remaining in the battery at the time it was charged and will not discharge below that point. The result of the memory effect is that the energy storage capacity of the battery is reduced. Other significant advantages of lithium ion batteries are that they are lightweight, have a high energy storage capacity and higher voltage per cell than other batteries. This makes for a battery that is useful in small portable electronic equipment, e.g., wireless mobile telephones and notebook computers.
Due to the unique chemical structure and chemical reaction of lithium ion batteries, the batteries can be dangerous if over discharged or overcharged. Over discharging and overcharging of lithium ion batteries can cause an abundance of heat to be generated by the chemical reaction occurring in the battery. This abundance of heat can cause the lithium ion battery to become hot, catch fire or, explode. For this reason, circuitry is built into the lithium ion battery to monitor the temperature, voltage, and current drain of the battery. This circuitry will cut off power supplied by the lithium ion battery if the current drawn from the battery rises above a threshold level or the lithium ion battery voltage falls below a threshold level. The circuitry will also cut off power supplied to the lithium ion battery during charging if the voltage of the battery rises above a threshold level. Circuitry may also be included in the charger or a device connected to the battery to monitor charging and discharging of the lithium ion battery. This circuitry is required for each cell of a lithium ion battery adding to the cost of lithium ion batteries.
Lithium ion batteries are ideally suited for portable electronic equipment due to their small size and high energy densities. Portable electronic equipment generally draws relatively low current for sustained periods of time. Lithium ion batteries are not suitable for other portable equipment, e.g., cordless power tools, because these devices require a great amount of current when performing work, e.g., driving a screw with a cordless electric power drill. The required current would exceed the amount that lithium ion batteries can safely deliver creating a risk that the battery could become hot, catch fire, or explode.
The present invention provides an electrically heated smoking system which utilizes lithium ion batteries in a manner which allows high current to be delivered safely to the electrical resistance heating element during smoking of a cigarette.
The invention provides an electrical heated smoking system having a heater including at least one electrical resistance heating element wherein a lithium ion power source is electrically connected to the at least one electrical resistance heating element and a controller controls a flow of modulated pulses of electrical power from the lithium ion power source to the at least one electrical resistance heating element to prevent damage to the lithium ion power source.
The invention also provides a method for supplying electrical power to at least one electrical resistance heating element from a lithium ion power source and controlling the electrical power provided to the at least one electrical heating element by sending modulated pulses of electrical power from the lithium ion power source to the at least one electrical heating element thereby preventing damage to the lithium ion power source.